Genetics and human conception

Experimental evidence in a number of different in vivo and in vitro systems indicates clearly that the vertebrate oocyte is capable of repairing endogenous and exogenous DNA damaged as a result of meiotic recombination, the action of UV and X-irradiation or the effects of mutagenic chemicals. It would appear that both before and after the dictyate stage of meiosis the oocyte has less repair capacity and/or is more sensitive to DNA damaging agents. Epigenetic factors associated with the expression of genetic faults arising in oocytes have been largely ignored in the past. It is probable that attention to such factors, will in the future, lead to a better appreciation of the capacity of oocytes to repair genetic damage. Non-disjunctional events are particularly prone to occur in dictyate oocytes. Oxygen deprivation, perturbations of microtubular structure by temperature and other factors appear to have disastrous cytogenetic consequences at this otherwise resistant resting stage.